The present invention generally relates to heating apparatuses, and more particularly to a heating apparatus for use in chemical vapor deposition, annealing and the like when producing a semiconductor device.
There are various methods of heating when producing a semiconductor device. For example, there is a method which uses a lamp heater, a method which uses a high-frequency heater device, and a method which uses an electric heater made of graphite.
When using the lamp heater, a semiconductor wafer which is placed inside a process chamber is heated by irradiating an infrared ray from outside the process chamber via a light transmitting window which is formed in the process chamber. However, this method has a problem in that a reaction product within the process chamber becomes deposited on the light transmitting window, thereby gradually deteriorating the transmittance of the light transmitting window with time.
When using the high-frequency heater device, it is necessary to provide high-frequency coils within the process chamber. As a result, there is a problem in that the structure of the arrangement becomes complex. In addition, the power efficiency of this method is poor because of the indirect heating, and there is a problem in that the temperature cannot be raised quickly by this method.
The method which uses the electric heater made of graphite is one method which can eliminate the above described problems. The present invention relates to an improvement of a heating apparatus which uses an electric heater made of graphite when carrying out a heating process during production of a semiconductor device.
FIG. 1 shows a cross section of an example of a conventional heating apparatus using an electric heater made of graphite. In FIG.1, a process chamber 1 has a gas supply means 2 and a gas exhaust means 3, and an electric heater 13 made of graphite is provided within the process chamber 1. Ends of the electric heater 13 are connected to respective electrodes 6. A semiconductor wafer 15 is placed on a quartz plate 14, and this quartz plate 14 is provided on the electric heater 13. The electric heater 13, the quartz plate 14 and the electrodes 6 form an essential part of the heating apparatus.
FIG. 2 shows a plan view of the electric heater 13. As shown in FIG. 2, the electric heater 13 has a zigzag pattern which generally exists within a circular boundary.
Accordingly, the semiconductor wafer 15 is heated by the electric heater 13 having the zigzag pattern, and there is a problem in that the entire surface of the semiconductor wafer 15 cannot be heated uniformly. In addition, because the semiconductor wafer 15 is heated indirectly via the quartz plate 14, there is a problem in that the power efficiency is poor.